Oh bother - this is the picture I should have posted. That other one had a plain floor that shouldn't have been there. The reflections are clearer in this one.

A little quiz... how many raytrace bounces can you see in this image? Look carefully at the right sphere!

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)